with descriptions of new Species. 333 
bent, not particularly stout, and sometimes slightly inclined to 
fusiform, but tapering pretty gradually to a sharp point at one 
end; the other furnished with a well-defined globular head ap- 
proaching to ovate with generally a terminal point. 
This appears to be the most destructive species to oyster-shells, 
and abounds in the Frith of Forth. It is undoubtedly the C. 
celata of Grant: the form and large size of the spicula are suffi- 
cient to distinguish it. The C. celata of Dr. Johnston, however, is 
most likely another species, as the spicula are somewhat different. 
C.insidiosa. Pl. XV. fig. 5. 
Sponge when dry of a brown colour, branched ; the branches 
about 3-ths of an inch thick, irregular, anastomosing : papillee 
distant, irregularly arranged, rather small. Spicula ;4,th of 
an inch long, stout, sometimes shghtly fusiform, but generally 
tapering gradually to a fine sharp poimt at one end, towards 
which it is generally slightly bent ; the other extremity is fur- 
nished with a large globular head separated from the shaft by a 
distinct dusky line, and mostly a little flattened like the head of 
a pin. | 
tohis species, which occurs in Tridacna gigas, appears related to 
C. gorgonioides ; like it this has only one kind of spicula, and in 
both they are furnished with a rounded head. A cross section 
of the excavations of this form has much the appearance of a 
similar view of those of that species. I have not been able to 
trace the terminations of the cavities, and therefore cannot speak 
to their form. The short, stout spicula of C. insidiosa with their 
large pin-like head are very characteristic, and readily distinguish 
it from its congeners. 
C. gorgomotdes. Pl. XIV. figs. 1 & 6. 
Sponge of a brownish yellow colour, branched, anastomosing ; 
the principal branches stout, sometimes nearly 3th of an inch 
thick, irregularly rounded, or depressed, placed somewhat par- 
allel to each other, and much zigzaged, giving off lateral 
branches at the angles, which branches unite with those ad- 
joining: terminal twigs thin, tapering to a fine point and bifur- 
cating: papille large, frequently almost ;1,th of an inch in dia- 
meter, penetrating the surface of the shell or other matrix with- 
out apparent order, and placed considerably apart from each 
other. Spicula very numerous, large and stout, measuring ,/,th 
of an inch in length ; at one end there is an oval swelling which 
is frequently some little distance from the extremity : from thence 
the shaft gradually tapers to the other end, which is sharply 
pointed and is generally much bent, particularly towards the 
